1. It's Aeria
2. A GM can be "invisible" per say and you wouldn't know if he was watching you or not. This being said, he could've been lurking in the Co-Op channel checking all single player co-op rooms to make sure that player is playing legit. Yes, he can do that, and yes he can do it without you even noticing.
3. Quit, who cares. It will only make the game better by another hacker giving up. I'm glad they're doing something to finally make you hackers quit.
4. If Aeria even suspects you as hacking, they may ban you. Like if you're really good, they will ban you. Like if you never do bad in a game, ever, they will ban u. That's just how it is.